Oxidation kinetics of a Ni-Cu based cermet at high temperature
Résumé
The oxidation kinetics of a cermet composed of Ni-Cu alloy and nickel ferrite was studied by thermogravimetry at 960 °C under oxygen in the range 0.5-77 kPa. After an initial mass increase up to 15 g/m2 due to oxidation of surface metallic particles, the mass change was attributed to both outwards NiO growth and internal oxidation. Above 40 g/m2, the NiO scale thickness remained constant and the oxidation kinetics followed a complete parabolic law. The variations of the kinetic rate with oxygen partial pressure allowed to propose mechanisms, rate-controlling steps and kinetic laws in both transient and long term oxidation periods.
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